Through a crop-based biodiversity, natural resources and animals (birds, fruits, and forests), Tropical Asia is economically and physiogeographically rich. There are 16 countries of Tropical Asia ranging in size from around 610 km² (Singapore) to 3,000,000 km² (India). Its population, is dominantly rural—however, in 1995, a census showed that a region with 6 out of 25 of the large cities. The population is 1.6 billion, likely to reach 2.4 billion in 2025. Climate in Tropical Asia is subject to seasonal weather patterns with the two monsoons and the amount of tropical cyclones in the three core areas of cyclogenesis (the Bay of Bengal, north Pacific Ocean and South China Sea). The climate varies over several environmental factors such as: growing urbanization, land industrialization and economic development or the opposite land degradation, environmental issues, and increased pollution.